Toxic chemicals can be effective at very low concentrations and are usually colorless and odorless in the form of gas or vapors. Some toxic chemicals can be classified as non-persistent and their effects drop off after hours or minutes.
Other toxic chemicals can be classified as persistent and have a relative low vapor pressure and are usually delivered as liquid droplet particles or aerosols. Their effects can last for a week or more in such liquid and/or particulate forms.
Low vapor pressure toxic chemicals are recognized as threats by both military and Homeland Security agencies. These chemicals exhibit vapor pressures on the order of 10−6 to 10−8 torr, (where, a torr is equal to the pressure required to raise a column of mercury 1 mm) and can exist as either liquid droplets or solid particulates, and present an inhalation threat as an aerosol and a contact threat as surface particulates and/or droplets.
Sorbent tubes have been used for over a decade to collect vapor phase samples as well as solid phase micro-extraction (SPME) fibers. However, neither of these vapor collection technologies is capable of collecting aerosols or particulates on surfaces. Aerosol collection can be performed using either a filter based collector where the aerosols are trapped by the fibrous nature of the filter or a cyclonic type of collector where the different sized particulate samples are concentrated and separated by the use of an air cyclone. Currently particulate samples are collected using specialized wipes that are designed to collect particles from surfaces based on electrostatic attraction between the wipe and the particulates. None of these systems is capable of collecting all forms of target analyte; aerosols, and particulates on surfaces, and vapors in the air, and being easily interfaced with analytical instruments.
Because of their extremely low vapor pressures, low vapor pressure toxic chemicals cannot be detected using state-of-the-art chemical agent detectors, which all require that the sample be in the vapor phase for detection. Therefore, there exists a need for the capability to collect these toxic aerosols and particulates on surfaces as well as the more volatile chemicals existing as vapors using a common collection platform that can be integrated into various chemical agent detectors for ease of delivery of vapors (of the low vapor pressure toxic chemicals) for analysis.